This invention relates to a method of making 3,5-dichloro-p-toluoyl chloride ("DCTOC," also called "3,5-dichloro-4-methylbenzoyl chloride") by reacting 3,5-dichloromethyltoluate ("DCMT," also called "methyl-3,5-dichloro-4-methylbenzoate") with an .alpha.,.alpha.,.alpha.-trichloromethylbenzene. In particular, it relates to the use of ammonium septamolybdate, (NH.sub.4).sub.6 Mo.sub.7 O.sub.24.4H.sub.2 O (ASM), or ammonium dimolybdate, (NH.sub.4).sub.2 Mo.sub.2 O.sub.7.2H.sub.2 O (ADM), as the catalyst in that reaction. (The amounts of water of hydration may vary.)
In U.S. Pat. No. 4,080,378 toluoyl chloride is made by reacting p-toluylic acid methyl ester with 1,4-bis-(trichloromethyl)-benzene and p-chlorobenzoyl chloride is made by reacting p-chlorobenzoic acid methyl ester with p-chlorobenzotrichloride. In both reactions, the catalyst is molybdenum trioxide (MoO.sub.3).